The present invention relates to a steer angle control system for providing a wheeled vehicle with desired steering response characteristics.
One conventional steer angle control system is disclosed in a Japanese patent provisional publication No. 61-175180 corresponding to the abovementioned U.S. application No. 823,324 (U.S. Pat. No. 4,706,771).
This control system is provided with first and second reference mathematical models representing desired vehicles having desired dynamic characteristics and first and second actual mathematical models representing an actual vehicle to be controlled. In response to sensed values of the steering wheel angle and the speed of the controlled vehicle, this control system determines a desired value of a yawing motion variable by using the first reference model and separately determines a desired value of a side slipping motion variable by using the second reference model. Then, the control system determines a first optimum steer angle value by inputting the desired value of the yawing motion variable into the first actual model and a second optimum steer angle value by inputting the desired value of the side motion variable into the second actual model. Finally, the control system determines a weighted average of the first and second optimum angle values and steers the wheels of the controlled vehicle in accordance with the weighted average. In this way, this control system can provide an adequate steer angle control by adjusting the weights of the yawing motion and side slipping motion.
However, this conventional control system must solve the two reference mathematical models and the two actual mathematical models with a microcomputer mounted on the controlled vehicle. Therefore, the time required to complete each control cycle is so long that it is very difficult to implement an accurate control.